Dampening device for a rotary printing press

ABSTRACT

There is disclosed a dampening device for a rotary printing press, particularly for an offset rotary printing press, the dampening roller of which device applies moisture uniformly and constantly to the plate cylinder of the press, irrespective of the specific properties and dimensions of the coacting components of the device as may be present or develop during operation. For this purpose the dampening roller is frictionally driven by a coacting roller and engaged by this roller only at peripheral areas which are not in contact with ink-coated printing surfaces on the plate cylinder. Said peripheral areas are in the form of two circumferential collars or ribs at opposite ends of the inkcoated area of the plate cylinder.

United States Patent [72] lnventor Werner Koch Gotzenhain Uber Langen, Germany [211 Appl. No. 714,272

[54] DAMPENING DEVICE FOR A ROTARY PRINTING PRESS 7 Claims, 3 Drawing Figs.

[52} U.S.C1 101/147, 29/123 [51] 1nt.Cl 1341123/00 [50] FieldolSearch 101/147,

148, 348--352. 252, 216, (Track Digest), 367

[5 6] References Cited UNITED STATES PATENTS 2,207,460 7/ 1940 Hotchkiss ..1.0l./(Track Digest) 2,331,980 10/1943 Hoffman et a1. 118/262 Primary ExaminerRobert E. Pulfrey Assistant ExaminerEugene 1-1. Eickholt Attorney-Hane & Baxley' ABSTRACT: There is disclosed a dampening device for a rotary printing press, particularly for an offset rotary printing press, the dampening rollerof which device applies moisture uniformly and constantly to the plate cylinder of the press, irrespective of the specific properties and dimensions of the coacting components of the device as may be present or develop during operation. For this purpose the dampening roller is frictionally driven by a coacting roller and engaged by this roller only at peripheral areas which are not in contact with ink-coated printing surfaces on the plate cylinder. Said peripheral areas are in the form of two circumferential collars or ribs at opposite ends of the ink-coated area of the plate cylinder.

PATENTED JANTQIQYI 3556005 Fig. 3

Inventor.-

\AE KNER. kocH BY g A i 1 DAMPENING Davies son A ROTARYVPRINTING PRESS The invention relates to, a dampener for a rotary printing press, especially an offset rotary printing press, and more particularly to a dampener which includes at least one dampening roller in contact with the plate cylinder of the press, and moisture being transferred to the dampening roller by a coacting roller driven at substantially the same circumferential speed as the plate cylinder.

The dampening roller is usually driven by a friction drive which is derived via engaging peripheral surfaces of the plate cylinder and the dampening roller or via engaging peripheral surfaces of the dampener roller and a driving roller. The driving force applied to the dampener roller depends on the contact pressure between the dampener roller and the plate cylinder or between the dampener .roller and the driving roller. It also depends on the surface conditions on the plate cylinder, the drive roller, the dampener roller, and on the properties of moisture and ink on the printing plate secured to the plate cylinder. a

As is evident, "theaforementioned factors are inherently variable. Accordingly, theapplication of a definite constant drive to the dampening roller is not assured, especially when the gap of the plate cylinder is passed by the dampening roller. Constancy and-uniformity of the transferof moisture to the plate cylinder presenta problem which has long plagued the printing industry. Several attempts, none fully satisfactory, have been made to solve the problem. There is disclosed, for instance, in US." Pat. No. 3,296,964 a dampening roller mechanism for anoffset printing press in which a dampening roller with a relatively soft elastic surface'for dampening the printing surface of the plate cylinder is mounted in rolling contact with the plate cylinder on an axis parallel therewith. A hard cylindrical bearer is provided adjacent, each end of the plate cylinder and is rotative with the cylinder on a common axis. The mechanism also comprises a cylindrical truck adjacent each end of thedampening roller and rotative with the dampeningroller' on a common axis. The trucks have a relatively hard elastic contact surface in frictional rolling engagement with the respective bearers. The sum of the diameters of the plate cylinder and the roller slightly exceeds the sum of the diameters of each bearer and its associated truck, whereby the roller contacts theplate cylinder before thetrucks contact the bearers during advancement of the roller toward the plate cylinder. The contact pressure between thedampening roller and the plate cylinder iscontrolled by the pressure between the trucks and the respective bearers.

r The inherent difficulty with such mechanism is that is presupposes a constant thickness of the printing plate, that is.

that the sum total of the thickness of the printing plate and the thickness of the packing are constant. In actual practice, such constancy cannot be maintained. For instance, for multicolor printing, it is necessary to change the thickness of the packing for correcting the printing. Such change requires corresponding changes in the diameters of the trucks to maintain a pressure between the dampening roller and the plate cylinder, which has been found to constitute an optimal value. As is apparent, exchange of the trucks whenever the thickness of the packing is to be changed is highly inconvenient in practice, quite apart from causing a marked increase in costs.

It is a broad object of the invention to provide a novel and improved dampening device for a rotary printing press in which the dampening roller applies moisture to the plate cylinder of the press at a uniform and constant rate, without requiring an exchange of components of the device.

A more-specific object of the invention is to provide a novel and improved dampening device of the general kind abovereferred-to in which the dampening roller is driven by a friction drive, the efficiency of which is independent of the specific properties ofthe printing plate, the diameter of the plate cylinder, the material used as sleeve for the dampening 2 less coated with ink. Sleeves for dampening rollers are generally made of fabric or rubber, and as is evident, the friction coefficient at the sleeves of dampening rollers is bound to "be markedly different for fabrics than it is for rubber.

The aforepointed out objects, features and advantages and other objects, features and advantages' which will be pointed out hereinafter are" obtained by providing on the peripheral surface of the dampening roller circumferential ribs or collars which are disposed outside the circumferential area of the dampening roller which is and must be in contact with the ink coated area of the printing plate during operation. The dampening roller is frictionally driven by a driving roller the length of which is such that the driving roller is always in rotation transmitting frictional engagement with at least one of said ribs or collars. As a result, the dampening roller is no longer driven by the plate cylinder also, but solely by the driving roller. Moreover, the frictional driving force is applied only at peripheral surfaces which are not covered with ink due to con tact with the inked printing plate on the plate cylinder. Accordingly, the effective friction coefficient between the dampening roller and the driving roller remains constant. Hence, if the thickness of the printing plate on the plate cylinder or the thickness of the packing changes, no changes in the radial dimensions of the ribs or collars at the ends of the dampening rollers need to be made.

The driving roller is preferably a roller which is mounted for axial reciprocation, the stroke of the axial displacement of the roller being preferably such that the driving roller remains in contact with both ribs or collars in its axial limit positions. Such contact with both ribs or collars assures a uniform and reliable drive of the dampening roller.

In the accompanying drawing, a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a diagrammatic view, partly in section, of a dampening device according to the invention, the dampening roller being shown in contact with the plate cylinder and the driving roller being shown in its middle position;

FIG. 2 is a view similar to FIG. 1, thedriving roller being shown in its right-hand end position; and

of the invention.

roller, the contact pressure between the dampening roller and the plate cylinder and changes in the friction coefficient of the sleeveon the dampening roller as the same becomes more or Referring now to the FIGS. more in detail, a plate 3 is arranged upon a plate cylinder 1 and secured thereto in a conventional manner. A packing 2 is interposed between the printing plate and the peripheral surface of cylinder 1, also in a conventional manner. The total radial thickness of packing 2 and plate 3 will vary as it depends upon the specific requirements of the'printing operation to be carried out. The total thickness of components 2 and 3 can be measured in a conventional manner by means of the accurately machined bearers at the ends of the plate cylinder. A peripheral groove 15 is provided between each bearer 4 and the adjacent ends of packing 2 and plate 3 for a purpose which will be more fully explained hereinafter.

The exemplified dampening device comprises a dampening roller 5. The roller as shown has a rigid core 6 such as a metal core about which is wrapped and suitably secured a sleeve 7 such as a rubber sleeve. The sleeve is formed at both ends with radially protruding circumferential ribs or collars 8 and 9. The ribs are shown as being formed out of the material of the sleeve, but the ribs can also be secured to the sleeve or be formed directly on core 6 or secured thereto.

The axial spacing between the ribs or collars 8 and 9 is such that when the dampening roller 5, is in contact with the plate cylinder 1, the collars 8 are placed outside the area of the printing plate, and the central area-that is, the effective peripheral surface of roller 5-is in contact with the printing plate 3. As is clearly shown in the FIGS., collars 8 and 9 are disposed in radial registry with grooves 15. The diameter and width of the collars are such that the same do not engage at any time the peripheral surface of printing plate 3.

Rotation of dampening roller 5 is effected by frictional engagement of a driving roller with collars 8 and 9. Driving roller 10 should be visualized as being supplied with moisture by any suitable and conventional means (not shown) and transfers such moisture to the dampening roller. The moisture may be pure water or water to which a suitable additives such as alcohol are added.

Drive means for roller 10 and means for applying moisture thereto are generally known in the art and do not constitute part of the invention.

The distance between the axis of driving roller 10 and driven dampening roller 5 is such that the frictional engagement between ribs or collars 8 and 9 and the circumferential surface of roller 10 is sufficient to drive roller 5 and to transfer moisture.

Driving roller 10 is preferably positively coupled with plate cylinder 1 by a transmission means (not shown) such that any increase or decrease in the r.p.m. of the plate cylinder 1 causes simultaneously a corresponding increase or decrease in the r.p.m. of driving roller 10, and thus also of dampening roller 5.

Transmission means suitable for the purpose are generally known and do not constitute part of the invention.

The driving roller 10 is preferably mounted for axial reciprocation. Accordingly, the roller is subjected, in addition to a rotational movement, to the axial periodic movements indicated in the three FIGS. which show the driving roller in its two limit positions. and also in its middle position.

Driving means for applying a combined axial and rotational movement to a roller or cylinder are, of course, widely known and do not constitute part of the invention.

It is only essential for the understanding of the invention to point out that the stroke length of roller 10 is such that in either limit position the roller remains in driving engagement with at least one of the ribs or collars 8, 9 but preferably both ribs or collars, as is showri in FIGS. 2 and 3 by indicating the half stroke 11 of the roller 10.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore,

to cover all such changes and modifications in the appended claims.

lclaim:

l. A dampening device for a rotary printing press including a rotary plate cylinder, said device comprising in combination:

a rotary plate cylinder having thereon an axially elongate peripheral ink-coated area a peripheral groove adjacent to each end of the ink-coated area thereon;

a dampening roller having a central peripheral moisture carrying area the axial length of which is substantially coextensive with said ink coated area. said roller being rotatable parallel to the plate cylinder and positioned relative to said cylinder so that the moisture carrying area and the ink coating area are in substantial registry and in peripheral contact with each other;

a pair of collars mounted on opposite ends of the dampening roller axially outside the moisture carrying area thereon, the peripheries of said collars being radially aligned with said grooves and spaced apart from the plate cylinder; and

a driving roller rotatable parallel to the dampening roller and in rotation transmitting frictional engagement with at least one of said collars.

2. A dampening device according to claim 1 wherein said driving roller is mounted for axial reciprocation with reference to said dampening roller, the length of the driving roller being such that the roller is in rotation transmitting frictional engagement with one of said collars in any position of axial displacement with reference to the dampening roller.

3. A dampening device according to claim 2 wherein the length of the driving roller is such that the roller is in rotation transmitting frictional engagement with both collars in any position of axial displacement with reference to the dampening roller.

4. A dampening device according to claim I wherein the outer diameter of said collars is in excess of the outermost diameter of the circumferential moisture carrying area of the dampening roller between said collars.

5. A dampening device according to claim 1 wherein said dampening roller comprises a rigid core and a sleeve of comparatively elastic material encompassing said core, said collars being at the end of the sleeve.

6. A dampening device according to claim 5 wherein said collars are made in one piece with the sleeve material.

7. A dampening device according to claim 6 wherein said sleeve and the collars thereon are made of rubber. 

1. A dampening device for a rotary printing press including a rotary plate cylinder, said device comprising in combination: a rotary plate cylinder having thereon an axially elongate peripheral ink-coated area a peripheral groove adjacent to each end of the ink-coated area thereon; a dampening roller having a central peripheral moisture carrying area the axial length of which is substantially coextensive with said ink coated area, said roller being rotatable parallel to the plate cylinder and positioned relative to said cylinder so that the moisture carrying area and the ink coating area are in substantial registry and in peripheral contact with each other; a pair of collars mounted on opposite ends of the dampening roller axially outside the moisture carrying area thereon, the peripheries of said collars being radially aligned with said grooves and spaced apart from the plate cylinder; and a driving roller rotatable parallel to the dampening roller and in rotation transmitting frictional engagement with at least one of said collars.
 2. A dampening device according to claim 1 wherein said driving roller is mounted for axial reciprocation with reference to said dampening roller, the length of the driving roller being such that the roller is in rotation transmitting frictional engagement with one of said collars in any position of axial displacement with reference to the dampening roller.
 3. A dampening device according to claim 2 wherein the length of the driving roller is such that the roller is in rotation transmitting frictional engagement with both collars in any position of axial displacement with reference to the dampening roller.
 4. A dampening device according to claim 1 wherein the outer diameter of said collars is in excess of the outermost diameter of the circumferential moisture carrying area of the dampening roller between said collars.
 5. A dampening device according to claim 1 wherein said dampening roller comprises a rigid core and a sleeve of comparatively elastic material encompassing said core, said collars being at the end of the sleeve.
 6. A dampening device according to claim 5 wherein said collars are made in one piece with the sleeve material.
 7. A dampening device according to claim 6 wherein said sleeve and the collars thereon are made of rubber. 